The basic reason for any file compression is to shrink a large file into the smallest size. The biggest challenge to any file compression (both document and image) is that the file(s) have to be compressed to the smallest size without compromising the image quality or losing any image or data. To achieve this, lossless compression method is used. While choosing a good compression method it is necessary to ensure that the method does not degrade the input data. This is because usage of any compression method does alter the databits. Therefore it is important to validate that the method does not degrade the original data in any way.
To find out whether the compression system is enhancing or degrading the original data, it is necessary to compare the fidelity of both the original data and compressed data with a recognition system, such as OCR (optical character recognition). By using the OCR, it is possible to validate
whether the recognition rates for the compressed data are as high as those for the original input data.
Whether the compressed document is a scanned document or electronic based, the OCR extracts text from the file(s) (which may also contains images) and makes them searchable and editable. The best file format for file compression with OCR is the PDF file format for it can be compressed automatically, and it can be made seamlessly text-searchable for immediate file retrieval.
There are two types of file encounter when the PDF file is OCRd.
In the first type, the PDF file(s) appears the same as the source file. But an extra layer of text content will be added to the PDF. A transparent layer of text will be placed in the same position as the original scanned image that includes the text. Though the image may look a little grainy the text is still searchable.
In the second type, all the text that are recognized by the OCR are extracted from the source file and are converted to real text and are formatted, so that it can appear as close to the source file as possible. Editing text in this kind of OCRd PDF is much easier than any other file format.